Non-contact position sensor

ABSTRACT

The length in the direction of movement of a magnet is effectively used for position detection without using a gap of a stator, where the magnet moves, as a magnetic path. According to a proportion of the slider ( 110 ), having a magnet ( 111 ), that enters into a region where the slider is movable with a predetermined gap maintained between the stator ( 120 ) made from a magnetic body, a magnetism sensor ( 130 ) provided at a stator ( 120 ) detects the position of a slider ( 110 ). A magnetic flux leakage prevention member ( 140 ) prevents leakage of magnetic flux caused by that portion of the magnet ( 111 ) that has not entered in the region.

TECHNICAL FIELD

The present invention relates to a non-contact position sensor, forexample, a position sensor used for an EGR (Exhaust Gas Recirculation)control valve, which is applicable as a position sensor used in avariety of actuators.

BACKGROUND OF ART

In prior art, there was used a contact type position sensor having aresistive element and a brush slipping on the resistive element, as theposition sensor used in the EGR control valve. Recently, it has beenrequired that such a position sensor is used under severer workingcircumstances or for years.

Against such requirements, however, the contact type position sensor haspossibilities of occurrence of silicon compounds due to irruption ofsiloxane gas, sticking of abrasion powder caused by the brush actingminutely at high-G frequencies, or obstructed positional detection dueto increasing of contact resistance caused by the sticking of abrasionpowder on a contact area of the brush.

Additionally, as the brush slides on a resistant layer, abrasion of asliding area is unavoidable, so that there is a limit in the number ofoperations of the sensor.

Therefore, according to the conventional contact type position sensor,it is difficult to meet the above requirements.

In this view, the need of employing a non-contact type position sensorhaving no contact area has been increased.

As the non-contact sensor like this, a sensor using a hall sensor hasbeen developed. Thus, there are one sensor that utilizes a magnet formedwith one pole in a moving direction and further uses, as a magneticpath, a gap of a stator where the magnet moves as described in JapanesePatent Publication No. 3264929, and another sensor that utilizes amagnet formed with two poles (N, S) in a moving direction and arranges astator so to oppose one side of the magnet as described in JapanesePatent Laid-Open No. 2001-74409.

DISCLOSURE OF THE INVENTION

In the former non-contact sensor, however, it is necessary to narrow thegap of the stator, which is utilized as a magnetic path, as possiblebecause a broader gap of the stator would accelerate an escape ofmagnetic flux. However, if narrowing the gap of the stator, then themagnet becomes thin to cause its magnetic force to be reduced.

Consequently, it is required to adopt a rare-earth sintered magnethaving strong magnetic force as the magnet for sensor. Thus, there existproblems that the magnet is elevated in its cost and is breakable forvibrations due to its thinness. Additionally, it is difficult to combinea magnet with a shaft for detecting the position.

In the latter non-contact sensor, its usable range is shortened inrelation to a moving span of the magnet due to an insensible zonebetween two (N and S) poles. Additionally, if the sensor is providedwith a single-loop structure in view of shortening the moving span, thena splice in characteristics is produced in the vicinity of a center inthe moving direction, making linearity in characteristics worse.

In order to solve the above-mentioned problems, an object of the presentinvention is to provide a non-contact position sensor capable ofeffectively using a length of a magnet in its moving direction in orderto detect a position of the magnet with no use of a gap between themagnet and a stator as a magnetic path.

According to a first aspect of the present invention, a non-contactposition sensor comprises: a slider having a magnet; a stator consistingof a magnetic body having an area allowing the slider to move whilekeeping a predetermined clearance; a magnetically-sensitive sensorprovided in the stator to detect a position of the slider correspondingto a percentage of the magnet entering the area; and a magnetic fluxleakproof member for preventing magnetic flux, which is generated in apart of the magnet that does not enter the area, from leaking out to thestator.

According to a second aspect of the present invention, a non-contactposition sensor comprises: a slider having a magnet having its front andback faces whose polarities are different from each other; a statorconsisting of a magnetic body having a pair of opposed walls forming anarea allowing the slider to move while keeping a predeterminedclearance, the opposed walls corresponding to the front and back facesof the magnet; a magnetically-sensitive sensor provided in the stator todetect a position of the slider corresponding to a percentage of themagnet entering the area; and a magnetic flux leakproof member forpreventing magnetic flux, which is generated in a part of the magnetthat does not enter the area, from leaking out to the stator.

According to a third aspect of the present invention, a non-contactposition sensor comprises: a slider having a magnet having its front andback faces whose polarities are different from each other; a main statorconsisting of a magnetic body having a pair of opposed walls forming anarea allowing the slider to move while keeping a predeterminedclearance, the opposed walls corresponding to the front and back facesof the magnet, and a gap continuing into the opposed walls; amagnetically-sensitive sensor arranged in the gap to detect a positionof the slider corresponding to a percentage of the magnet entering thearea; and an assist stator for preventing magnetic flux, which isgenerated in a part of the magnet that does not enter the area, fromleaking out to the main stator.

According to a fourth aspect of the present invention, a non-contactposition sensor comprises: a slider having a magnet having its front andback faces whose polarities are different from each other; a main statorconsisting of a magnetic body having a pair of opposed walls forming afirst area allowing the slider to move while keeping a predeterminedclearance, the opposed walls corresponding to the front and back facesof the magnet, and a gap continuing into the opposed walls; an assiststator arranged at a gap extending along a moving direction of theslider from the main stator, the assist stator consisting of a magneticbody having a pair of opposed walls forming a second area allowing theslider to move while keeping a predetermined clearance; and amagnetically-sensitive sensor arranged in the gap of the main stator todetect a position of the slider corresponding to a percentage of themagnet entering the first area of the main stator.

According to a fifth aspect of the present invention, a non-contactposition sensor comprises: a slider having a magnet having its front andback faces whose polarities are different from each other; a main statorconsisting of a magnetic body having a pair of opposed walls forming afirst area allowing the slider to move while keeping a predeterminedclearance, the opposed walls corresponding to the front and back facesof the magnet, and a pair of transverse walls formed to extend from theopposed walls and arranged close to each other through a uniform gapalong a moving direction of the slider; an assist stator arranged at agap extending along the moving direction of the slider from the mainstator, the assist stator consisting of a magnetic body having a pair ofopposed walls forming a second area allowing the slider to move whilekeeping a predetermined clearance, the opposed walls corresponding tothe front and back faces of the magnet; and a magnetically-sensitivesensor arranged in an optional position in the gap of the main stator todetect a position of the slider corresponding to a percentage of themagnet entering the first area of the main stator.

According to a sixth aspect of the present invention, a non-contactposition sensor comprises: a slider having a magnet having its front andback faces whose polarities are different from each other; a main statorconsisting of a magnetic body having a pair of opposed walls forming afirst area allowing the slider to move while keeping a predeterminedclearance, the opposed walls corresponding to the front and back facesof the magnet, and a transverse arm formed to extend from one of theopposed walls and arranged close to the other of the opposed wallsthrough a uniform gap along a moving direction of the slider; an assiststator arranged at a gap extending along the moving direction of theslider from the main stator, the assist stator consisting of a magneticbody having a pair of opposed walls forming a second area allowing theslider to move while keeping a predetermined clearance, the opposedwalls corresponding to the front and back faces of the magnet; and amagnetically-sensitive sensor arranged in an optional position in thegap of the main stator to detect a position of the slider correspondingto a percentage of the magnet entering the first area of the mainstator.

According to a seventh aspect of the present invention, a non-contactposition sensor comprises: a slider having a magnet having its front andback faces whose polarities are different from each other; a main statorconsisting of a magnetic body having a pair of opposed walls forming afirst area allowing the slider to move while keeping a predeterminedclearance, the opposed walls corresponding to the front and back facesof the magnet, a first arm formed to extend from one of the opposedwalls and arranged close to the other of the opposed walls through auniform gap along a moving direction of the slider and a second armformed to extend from the other of the opposed walls and arranged closeto the one of the opposed walls through a uniform gap along a movingdirection of the slider; an assist stator arranged at a gap extendingalong the moving direction of the slider from the main stator, theassist stator consisting of a magnetic body having a pair of opposedwalls forming a second area allowing the slider to move while keeping apredetermined clearance, the opposed walls corresponding to the frontand back faces of the magnet; and a magnetically-sensitive sensorarranged in an optional position in the gap between the first arm andthe other of the opposed walls to detect a position of the slidercorresponding to a percentage of the magnet entering the first area ofthe main stator.

According to an eighth aspect of the present invention, a non-contactposition sensor comprises: a slider consisting of a pair of magnetswhose side edges along a moving direction of the slider are joined toeach other and each of which has front and back faces whose polaritiesare different from each other and an armature provided on one side faceof the pair of magnets; a main stator consisting of a magnetic bodyarranged in a position opposing the other side face of the pair ofmagnets; a magnetically-sensitive sensor provided in the main stator todetect a position of the slider corresponding to a percentage of themagnets entering an area where the slider opposes the main stator; andan assist stator consisting of a magnetic body for preventing magneticflux, which is generated in parts of the magnets that do not enter thearea, from leaking out to the main stator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is views typically showing a non-contact position sensor inaccordance with a first embodiment of the present invention, in whichFIG. 1( a) is a perspective view, FIG. 1( b) is a front view and FIG. 1(c) is a side view;

FIG. 2 is a perspective view typically showing the non-contact positionsensor having its part developed, in accordance with a second embodimentof the present invention, whose part is developed;

FIG. 3 is typical views showing a difference in situation of flux inbetween one case of having an assist stator and another case of havingno assist stator, in which FIG. 3( a) illustrates the case of having theassist stator and FIG. 3( b) illustrates the case of having no assiststator;

FIG. 4 is typical views showing a difference in situation of flux inbetween an integral-type assist stator having no gap and aseparation-type assist stator having a gap, in which FIG. 4( a)illustrates a case of the integral-type assist stator having no gap andFIG. 4( b) illustrates a case of the separation-type assist statorhaving the gap;

FIG. 5 is graphs about a quantity of magnetism of a sensing part andlinearity corresponding to the presence of an assist stator, in whichFIG. 5( a) illustrates the quantity of magnetism of the sensing part andFIG. 5( b) illustrates the linearity;

FIG. 6 is a perspective view typically showing the non-contact positionsensor having its part developed, in accordance with a third embodimentof the present invention;

FIG. 7( a) is a top view of the non-contact position sensor of FIG. 6,FIG. 7( b) is a longitudinal sectional and front view of FIG. 6 and FIG.7( c) is a bottom view of FIG. 6;

FIG. 8 is a perspective view typically showing the non-contact positionsensor having its part developed, in accordance with a fourth embodimentof the present invention;

FIG. 9 is a sectional view showing one example of applying thenon-contact position sensor of FIG. 8 to a position sensor for EGRvalve;

FIG. 10 is graphs showing a comparison of output characteristics of asensor using an integral-type assist stator with output characteristicsof a sensor using a separation-type assist stator, in which FIG. 10( a)shows the output characteristics adopting the integral-type assiststator and FIG. 10( b) shows the output characteristics adopting theseparation-type assist stator;

In sensors where each detecting position thereof is deviated from acenter of a main stator,

FIG. 11 is graphs showing a comparison of hysteresis characteristics ofa sensor using an integral-type assist stator with hysteresischaracteristics of a sensor using a separation-type assist stator, inwhich FIG. 11( a) shows the hysteresis characteristics adopting theintegral-type assist stator and FIG. 11( b) shows the hysteresischaracteristics adopting the separation-type assist stator;

In sensors where each detecting position thereof is established at acenter of a main stator,

FIG. 12 is graphs showing a comparison of hysteresis characteristics ofa sensor using an integral-type assist stator with hysteresischaracteristics of a sensor using a separation-type assist stator, inwhich FIG. 12( a) shows the hysteresis characteristics adopting theintegral-type assist stator and FIG. 12( b) shows the hysteresischaracteristics adopting the separation-type assist stator;

FIG. 13 is a perspective view typically showing the non-contact positionsensor having its part developed, in accordance with a fifth embodimentof the present invention;

FIG. 14( a) is a top view of the non-contact position sensor of FIG. 13,FIG. 14( b) is a longitudinal sectional and front view of thenon-contact position sensor of FIG. 13 and FIG. 13( c) is a crosssectional bottom view of the non-contact position sensor of FIG. 13;

FIG. 15 is a perspective view typically showing the non-contact positionsensor having its part developed, in accordance with a sixth embodimentof the present invention;

FIG. 16 is a sectional view showing one example of applying thenon-contact position sensor of FIG. 15 to a position sensor for EGRvalve;

In sensors where each main arm thereof has a width equal to that of anauxiliary arm,

FIG. 17 is graphs showing a comparison of hysteresis characteristics ofa sensor using an integral-type assist stator with hysteresischaracteristics of a sensor using a separation-type assist stator, inwhich FIG. 17( a) shows the hysteresis characteristics adopting theintegral-type assist stator and FIG. 17( b) shows the hysteresischaracteristics adopting the separation-type assist stator;

In the sensor using the separation-type assist stator shown in FIG. 17(b),

FIG. 18 is a graph showing the hysteresis characteristics of the sensorwhere the width of the auxiliary arm is narrowed;

In the sensor using the separation-type assist stator shown in FIG. 17(b),

FIG. 19 is a graph showing the hysteresis characteristics of the sensorwhere an interval between the main arm and the auxiliary arm isnarrowed;

FIG. 20 is an explanatory diagram showing a tendency about an effect ofa position of a detecting part on linearity;

FIG. 21 is an explanatory diagram showing a tendency about arelationship between the position of the detecting part and hysteresis;

FIG. 22 is an explanatory diagram showing a tendency about an effect ofa gap between a main stator and an assist stator on linearity;

FIG. 23 is an explanatory diagram showing a tendency about arelationship between the gap between the main stator and the assiststator, and hysteresis;

FIG. 24 is an explanatory diagram showing a tendency about arelationship between a gap of the assist stator and hysteresis;

FIG. 25 is views typically showing the non-contact position sensor inaccordance with a seventh embodiment of the present invention, in whichFIG. 25( a) is an entire perspective view of the sensor and FIG. 25( b)is a perspective view of a substantial part of the sensor;

FIG. 26( a) is a top view of the non-contact position sensor of FIG. 25,FIG. 26( b) is a side view of the non-contact position sensor of FIG. 25and FIG. 26( c) is a bottom view of the non-contact position sensor ofFIG. 25;

FIG. 27 is views typically showing the non-contact position sensorhaving its part developed, in accordance with an eighth embodiment ofthe present invention, in which FIG. 27( a) is an entire perspectiveview of the sensor and FIG. 27( b) is a perspective view of asubstantial part of the sensor; and

FIG. 28 is views typically showing the non-contact position sensorhaving its part developed, in accordance with a ninth embodiment of thepresent invention, in which FIG. 28( a) is an entire perspective view ofthe sensor and FIGS. 28( b) and 28(c) are perspective views of asubstantial part of the sensor.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described with reference todrawings.

FIG. 1 includes views typically showing a non-contact position sensor inaccordance with a first embodiment of the present invention, in whichFIG. 1( a) is a perspective view of the sensor, FIG. 1( b) is a frontview and FIG. 1( c) is a side view.

This non-contact position sensor 100 comprises a magnet 111 as a slider110, a main stator 121 as a stator 120, a hall sensor 131 as amagnetically-sensitive sensor 130, and an assist stator 141 as amagnetic flux leakproof member 140.

The magnet 111 is in the form of a substantially flat plate having anN-pole on one side of both front and back faces of the magnet and anS-pole on the other side and is constructed so as to move in alongitudinal direction of the magnet (i.e. a vertical direction shownwith arrow of FIG. 1( a)).

The main stator 121 consists of a magnetic body and includes a pair ofopposed walls 122, 124 corresponding to both surfaces of the magnet 111.A transverse wall 123 extending from one edge of the opposed wall 122toward the other opposed wall 124 and another transverse wall 125extending from one edge of the other opposed wall 124 toward the opposedwall 122 are arranged close to each other through a gap Gm at a midpointbetween the opposed walls 122, 124.

This gap Gm is formed uniformly between both ends of the main stator 121(upper and lower ends in FIG. 1) along a moving direction of the magnet111. The main stator 121 like this can be manufactured by pressing e.g.a plate material of magnetic material whose magnetic resistance is assmall as possible.

The hall sensor 131 is arranged in an appropriate position in the gap Gmof the main stator 121. For example, it is desirable to arrange thesensor 131 at a midpoint between both ends of the main stator 121 (inFIG. 1, at a center level between the upper end and the lower end of thestator 121). In this way, on the ground that the gap Gm of the mainstator 121 is provided to accommodate the hall sensor 131, it ispreferable that the gap Gm is formed to be a clearance as small as itcan accommodate the sensor 131.

The assist stator 141 consists of a magnetic body and includes a pair ofopposed walls 142, 144 corresponding to both front and back faces of themagnet 111. A transverse wall 143 extending from one edge of the opposedwall 142 toward the other opposed wall 144 and another transverse wall145 extending from one edge of the other opposed wall 144 toward theopposed wall 142 are arranged close to each other through a gap Ga at amidpoint between the opposed walls 142, 144.

This gap Ga is formed uniformly between both ends of the transversewalls 143, 145 (respective upper and lower ends in FIG. 1) along themoving direction of the magnet 111. In the assist stator 141, its lowerportions spreading from the transverse walls 143, 145 up to the opposedwalls 142, 144 are eliminated. Because these lower portions have lessimpact on characteristics of the sensor irrespective of their existence.The assist stator 141 like this can be manufactured by pressing e.g. aplate material of magnetic material whose magnetic resistance is assmall as possible.

The main stator 121 and the assist stator 141 are arranged close to eachother through a gap Gma along the moving direction of the magnet 111. InFIG. 1, since the assist stator 141 is positioned above the main stator121, a spatial area defined between the opposed walls 142, 144 of theassist stator 141 is arranged above a spatial area defined between theopposed walls 122, 124 of the main stator 121, continuously.

The non-contact position sensor 100 constructed above can detect aposition of the magnet 111 in a non-contact manner since the hall sensor131 detects magnetic flux corresponding to an entrance percentage of themagnet 111 in entering the area between the opposed walls 122, 124 ofthe main stator 121, the magnet 111 being movable throughout the areabetween the opposed walls 122, 124 of the main stator 121 and thesequent area between opposed walls 142, 144 of the assist stator 141.

Again, this non-contact position sensor 100 is preventive of fluxleakage since all flux generated from a part of the magnet 111 enteringthe area between the opposed walls 122, 124 of the main stator 121passes trough a magnetic path formed by the main stator 121.

While, since all flux generated from a part of the magnet 111 enteringthe area between the opposed walls 142, 144 of the assist stator 141passes trough a magnetic path formed by the assist stator 141, fluxleakage is prevented as well.

Thus, assuming that the moving direction of the magnet 111 isrepresented by e.g. Z-direction, any offset of the magnet 111 inX-direction or Y-direction perpendicular to the Z-direction would notinfluence on the magnetic paths, thereby causing no change in detectionoutputs of the hall sensor 131.

FIG. 2 is a perspective view typically showing the non-contact positionsensor having its part developed, in accordance with a second embodimentof the present invention. In this figure, elements similar to those ofFIG. 1 are indicated with the same reference numerals plus one hundredrespectively, and their overlapped descriptions are eliminated.

In this non-contact position sensor 200, a slider 210 comprises a sliderbody 212 accommodating a magnet 211 and a shaft 213 extending from theslider body 212 downwardly. Further, an assist stator 241 as a magneticflux leakproof member 240 is formed by opposed walls 242, 244 whose sideedges are connected with each other through a transverse wall 243integrally. Therefore, the assist stator 241 is constructed as anintegral part having no gap Ga of FIG. 1.

The non-contact position sensor 200 like this can detect a position of amagnet 211, namely, both positions of the slider body 212 and the shaft213 in a non-contact manner since a hall sensor 231 detects magneticflux corresponding to an entrance percentage of the magnet 211 inentering an area between opposed walls 222, 224 of a main stator 221,the magnet 211 of the slider 210 being movable throughout the areabetween the opposed walls 222, 224 of the main stator 221 and a sequentarea between the opposed walls 242, 244 of the assist stator 241.

Again, this non-contact position sensor 200 is preventive of fluxleakage since all flux generated from a part of the magnet 211 enteringthe area between the opposed walls 222, 224 of the main stator 221passes trough a magnetic path formed by the main stator 221.

While, since all flux generated from a part of the magnet 211 enteringthe area between the opposed walls 242, 244 of the assist stator 241passes trough a magnetic path formed by the assist stator 241, fluxleakage is prevented as well.

Thus, assuming that the moving direction of the magnet 211 isrepresented by Z-direction, any offset of the magnet 211 in X-directionor Y-direction perpendicular to the Z-direction would not influence onthe magnetic paths, thereby causing no change in detection outputs ofthe hall sensor 231.

Taking the non-contact position sensor 100 shown in FIG. 1 as anexample, FIG. 3 includes views typically showing that there exists adifference in situation of flux generated from the magnet 111 in betweenone case of having no assist stator 141 (FIG. 3( a)) and another case ofhaving the assist stator 141 (FIG. 3( b)). Similarly, FIG. 4 includesviews typically showing that there exists a difference in situation ofthe flux generated from the magnet 111 in between one case of the“integral-type” assist stator 141 having no gap Ga (FIG. 4( a)) andanother case of the “separation-type” assist stator 141 having the gapGa (FIG. 3( b)).

In each of FIGS. 3 and 4, for the sake of understanding, all of themoving direction of the magnet 111, the gap Gm of the main stator 121,the hall sensor 131, the gap Ga of the assist sensor 141 and the gap Gmabetween the main stator 121 and the assist stator 141 are illustrated onan identical plane. Then, the situations of flux shown with thesetypical views are substantially applicable to not only the non-contactposition sensor 200 of FIG. 2 but all of later-mentioned non-contactposition sensors 300, 400, 500, 600, 700, 800 and 900 similarly.

As shown in FIG. 3( a), it is obvious that in case of no assist stator141, part of flux close to the main stator 121, which is generated froma part of the magnet 111 that does not enter the main stator 121, entersthe main stator 121. This part of flux entering the main stator 121 hasan effect on linearity and hysteresis in the flux detection by the hallsensor 131.

Accordingly, it is noted that a change in flux detected by the hallsensor 131 is not proportional to an entrance length L of the magnet(part) 111 slotting into the main stator 121.

On the contrary, in case of the assist stator 141, the flux generatedfrom the part of the magnet 111 that does not enter the main stator 121enters the assist stator 141 and thus does not leak out into the mainstator 121, as shown in FIG. 3( b). Consequently, there is nopossibility that the flux generated from the part of the magnet 111 thatdoes not enter the main stator 121 has an effect on linearity andhysteresis in the detection of flux by the hall sensor 131.

Accordingly, a change in flux detected by the hall sensor 131 becomesproportional to the entrance length L of the magnet 111 entering themain stator 121, so that detecting accuracy of the non-contact positionsensor 100 is improved. Consequently, there is need to arrange theassist stator 141, undoubtedly.

Here, it is assumed that a magnetic resistance of the gap Gm of the mainstator 121 is represented by Rm and a magnetic flux of a gap Gma1between the main stator 121 and the assist stator 141 is represented byRma1. As shown in FIG. 4( a), when the assist stator 141 is integrallyformed with no gap Ga, a leakage of flux from the main stator 121 to theassist stator 141 is produced on condition of a relationship Rma1≦Rm.

Thus, in order to eliminate a leakage of flux between the main stator121 and the assist stator 141, it is necessary to satisfy a condition ofRma1>Rm.

On the other hand, as shown in FIG. 4( b), when the assist stator 141 isseparately formed with a gap Ga whose magnetic resistance is representedby Ra, a leakage of flux from the assist stator 141 to the main stator121 is produced on condition of a relationship Rm<Ra. Conversely, incase of a relationship Rm>Ra, a leakage of flux from the main stator 121to the assist stator 141 is produced. Further, in case of relationshipsRma2≦Rm, Ra, a leakage of flux is produced between the main stator 121and the assist stator 141.

Thus, in order to eliminate a leakage of flux between the main stator121 and the assist stator 141, it is necessary to satisfy a condition ofRma2>Rm=Ra.

Meanwhile, since it can be presumed that the leakage of flux from themain stator 121 to the assist stator 141 becomes smaller on condition ofRa>0 rather than Ra=0, there is established a relationship of Rma1>Rma2.Further, since it can be presumed that to get Rma larger has an effect(surge) on linearity, it is necessary to reduce Rma as possible. As aresult, it is obvious that a provision of the assist stator 141 with thegap Ga is desirable.

Nevertheless, even if providing no gap Ga, it is effective to providethe sensor with the assist stator 141, as mentioned above. Therefore,the present invention includes even a sensor having an assist stator(e.g. the assist stator 141) provided with no gap Ga.

FIG. 5 includes graphs concerning a quantity of magnetism of a sensingpart (FIG. 5( a)) and a linearity (FIG. 5( b)) corresponding to thepresence of the assist stators 141, 241. From these graphs, it will beunderstood that the quantity of magnetism of the sensing part getssmaller and the linearity becomes flatter in each of cases (shown withsolid lines) of having the assist stators 141, 241 due to no influencefrom the leakage of flux, in comparison with other cases (shown withbroken lines) without the assist stators 141, 241.

According to the above-mentioned non-contact position sensors 100, 200;

(1) with the use of the assist stators 141, 241, it is possible toprevent flux from leaking out to the outside;

(2) with the use of the assist stators 141, 241, it is possible todetect the positions of the magnets 111, 211 within their entireoperation ranges appropriately;

(3) it is possible to provide non-contact position sensors that arecompact in respective moving directions of the magnets 111, 211 inrelation to their moving spans;

(4) with the detection of flux at a center between both ends of the gapGm formed uniformly throughout both ends of the main stator 121 (221),it is possible to attain sensor characteristics exhibiting improvedlinearity and reduced hysteresis;

(5) by adjusting a balance between the gap Gm of the main stator 121(221) and the gap Gma formed between the main stator 121 (221) and theassist stator 141 (241), it is possible to correct and alter outputcharacteristics of the sensor;

(6) by determining the presence of the gap Ga of the assist stator 141(241) and adjusting a clearance of the gap Ga, it is possible to correctand alter output characteristics of the sensor; and

(7) since both of the main stator 121 (221) and the assist stator 141(241) are manufactured by press operations, it is possible to producethe sensor in a low price.

FIG. 6 is a perspective view typically showing the non-contact positionsensor having its part developed, in accordance with a third embodimentof the present invention. FIG. 7 shows a top view (FIG. 7( a)), alongitudinal sectional and front view (FIG. 7( b)) and a bottom view(FIG. 7( c)) of the sensor. In these figures, elements similar to thoseof FIG. 1 are indicated with the same reference numerals plus twohundreds respectively, and their overlapped descriptions are eliminated.

In a main stator 321 of this non-contact position sensor 300, atransverse wall 323 continuing to one opposed wall 322 is formed toextend over the other opposed wall 324 and further, the transverse wall323 and one edge of the opposed wall 324 are adjacent to each otherthrough a gap Gm. This gap Gm is formed uniformly throughout both ends(upper and lower ends in FIGS. 6 and 7) of the main stator 321 along amoving direction of the magnet 311.

A hall sensor 331 is arranged in an appropriate position in the gap Gmof the main stator 321. For example, it is desirable to arrange thesensor 331 at a midpoint between both ends of the main stator 321 (inFIGS. 6 and 7, at a center level between the upper end and the lower endof the stator 321). In this way, on the ground that the gap Gm of themain stator 321 is provided to accommodate the hall sensor 331, it ispreferable that the gap Gm is formed to have a clearance as small as itcan accommodate the sensor 331 although the gap Gm appears to beremarkably broad in the figure.

An assist stator 341 as a magnetic flux leakproof member 340 is formedby opposed walls 342, 344 whose side edges are connected with each otherthrough a transverse wall 343 integrally and therefore, the assiststator 341 is constructed as an integral part having no gap Ga.Additionally, the assist stator 341 is formed so that a lower part ofthe transverse wall 343 is level with those of the opposed walls 342,344 without removing the lower part of the transverse wall 343.

The non-contact position sensor 300 like this can detect a position ofthe magnet 311 in a non-contact manner since a hall sensor 331 detectsmagnetic flux corresponding to an entrance percentage of the magnet 311in entering an area between the opposed walls 322, 324 of the mainstator 321, the magnet 311 being movable throughout the area between theopposed walls 322, 324 of the main stator 321 and a sequent area betweenthe opposed walls 342, 344 of the assist stator 341.

Again, this non-contact position sensor 300 is preventive of fluxleakage since all flux generated from a part of the magnet 311 enteringthe area between the opposed walls 322, 324 of the main stator 321passes trough a magnetic path formed by the main stator 321.

While, since all flux generated from a part of the magnet 311 enteringthe area between the opposed walls 342, 344 of the assist stator 341passes trough a magnetic path formed by the assist stator 341, fluxleakage is prevented as well.

Thus, assuming that the moving direction of the magnet 311 isrepresented by Z-direction, any offset of the magnet 311 in X-directionor Y-direction perpendicular to the Z-direction would not influence onthe magnetic paths, thereby causing no change in outputs of the hallsensor 331.

FIG. 8 is a perspective view typically showing the non-contact positionsensor having its part developed, in accordance with a fourth embodimentof the present invention. In the figure, elements similar to those ofFIG. 6 are indicated with the same reference numerals plus one hundredrespectively, and their overlapped descriptions are eliminated.

In this non-contact position sensor 400, a slider 410 comprises a sliderbody 412 accommodating a magnet 411 and a shaft 413 extending from theslider body 412 downwardly. Further, in an assist stator 441 as amagnetic flux leakproof member 440, a transverse wall 443 extending fromone edge of one opposed wall 442 toward the other opposed wall 444 andanother transverse wall 445 extending from one edge of the other opposedwall 444 toward the opposed wall 442 are arranged close to each otherthrough a gap Ga at a midpoint between the opposed walls 442, 444.Additionally, in the assist stator 441, its lower parts extending fromthe transverse walls 443, 445 to the opposed walls 442, 444 areeliminated.

Again, on the ground that the gap Gm of the main stator 421 is providedto accommodate a hall sensor 431, it is preferable that the gap Gm isformed to have a clearance as small as it can accommodate the sensor 431although the gap Gm appears to be remarkably broad in the figure.

The non-contact position sensor 400 like this can detect a position ofthe magnet 411, namely, both positions of the slider body 412 and theshaft 413 in a non-contact manner since the hall sensor 431 detectsmagnetic flux corresponding to an entrance percentage of the magnet 411in entering an area between the opposed walls 422, 424 of the mainstator 421, the magnet 411 being movable throughout the area between theopposed walls 422, 424 of the main stator 421 and a sequent area betweenthe opposed walls 442, 444 of the assist stator 441.

Again, this non-contact position sensor 400 is preventive of fluxleakage since all flux generated from a part of the magnet 411 enteringthe area between the opposed walls 422, 424 of the main stator 421passes trough a magnetic path formed by the main stator 421.

While, since all flux generated from a part of the magnet 411 enteringthe area between the opposed walls 442, 444 of the assist stator 441passes trough a magnetic path formed by the assist stator 341, fluxleakage is prevented as well.

Thus, assuming that the moving direction of the magnet 411 isrepresented by Z-direction, any offset of the magnet 411 in X-directionor Y-direction perpendicular to the Z-direction would not influence onthe magnetic paths, thereby causing no change in detection outputs ofthe hall sensor 431.

FIG. 9 is a sectional view showing one example where the non-contactposition sensor 400 of FIG. 8 is applied to a position sensor for EGRvalve. This position sensor 450 for EGR valve includes the main stator421 and the assist stator 441 held by a stator holder 451 provided in asensor body. In the sensor 450, since the slider 410 accommodating themagnet 411 moves up and down in the figure, the hall sensor 431 detects,at its detecting position 432, a position of the magnet 411, that is,both positions of the slider body 412 and the shaft 413. In the figure,reference numeral 452 designates a connector terminal for connecting aterminal of the hall sensor 431.

FIG. 10 includes graphs showing a comparison of output characteristics(FIG. 10( a)) of the non-contact position sensor 300 using theintegral-type assist stator 341 having no gap Ga with outputcharacteristics (FIG. 10( b)) of the non-contact position sensor 400using the separation-type assist stator 441 having the gap Ga.

It is found that when employing the separation-type assist stator 441shown in FIG. 10( b), an output of the non-contact position sensor 400keeps to be larger than an output of the sensor in case of employing theintegral-type assist stator 341 shown in FIG. 10( a) and furthermore, adifference between the outputs gradually increases as the operation ofthe slider stroke proceeds. This is because an influence of magneticforce of the assist stator 441 on the main stator 421 increases due toseparation of an assist stator.

Provided that the detecting position is established in a positiondeviated from each center of the main stators 321, 421 toward each ofthe assist stators 341, 441 by an appropriate distance (e.g. 2 mm), FIG.11 includes graphs showing a comparison of hysteresis characteristics(FIG. 11( a)) of the non-contact position sensor 300 using theintegral-type assist stator 341 having no gap Ga with hysteresischaracteristics (FIG. 11( b)) of the non-contact position sensor 400using the separation-type assist stator 441 having the gap Ga.

From the figure, it is found that the sensor employing theseparation-type assist stator 441 shown in FIG. 11( b) exhibits smallerhysteresis and better linearity than those of the sensor employing theintegral-type assist stator 341 shown in FIG. 11( a).

Provided that the detecting positions are established at respectivecenters of the main stators 321, 421, FIG. 12 includes graphs showing acomparison of the hysteresis characteristics (FIG. 12( a)) of thenon-contact position sensor 300 using the integral-type assist stator341 having no gap Ga with the hysteresis characteristics (FIG. 12( b))of the non-contact position sensor 400 using the separation-type assiststator 441 having the gap Ga.

Also in this case, it is found that the sensor employing theseparation-type assist stator 441 shown in FIG. 12( b) exhibits smallerhysteresis and better linearity than those of the sensor employing theintegral-type assist stator 341 shown in FIG. 12( a).

In this way, despite of whether the detecting positions are at thecenters of the main stators 321, 421 respectively or deviated from thesame centers, the sensor employing the separation-type assist stator 441exhibits smaller hysteresis and better linearity than those of thesensor employing the integral-type assist stator 341. Therefore, it isfound that desirable hysteresis characteristics can be established byadjusting a separation clearance of the assist stator 441.

Additionally comparing FIG. 11( a) with FIG. 12( a) about the sensorseach employing the integral-type assist stator 341 in common, it isfound that one sensor where the detecting position is established at thecenter of the main stator 321 exhibits smaller hysteresis and betterlinearity than the other sensor where the detecting position is deviatedfrom the center of the main stator 321.

Comparing FIG. 11( b) with FIG. 12( b) about the sensors each employingthe separation-type assist stator 441 in common, it is found that onesensor where the detecting position is established at the center of themain stator 421 exhibits smaller hysteresis and better linearity thanthe other sensor where the detecting position is deviated from thecenter of the main stator 421.

In this way, despite of whether the assist stators 341, 441 are type ofintegral or separation, it is found that it is important to set thedetecting positions of the sensors at the centers of the main stators321, 421 respectively in order to reduce hysteresis and improvelinearity of the sensors.

According to the above-mentioned non-contact position sensors 300, 400;

(1) with the use of the assist stators 341, 441, it is possible toprevent flux from leaking out to the outside;

(2) with the use of the assist stators 341, 441, it is possible todetect the positions of the magnets 311, 411 within their wholeoperation ranges appropriately;

(3) it is possible to provide sensors that are compact in respectivemoving directions of the magnets 311, 411 in relation to their movingspans;

(4) with the detection of flux at a center between both ends of the gapGm formed uniformly throughout both ends of the main stator 321 (421),it is possible to attain sensor characteristics exhibiting improvedlinearity and reduced hysteresis;

(5) by adjusting a balance between the gap Gm of the main stator 321(421) and the gap Gma formed between the main stator 321 (421) and theassist stator 341 (441), it is possible to correct and alter outputcharacteristics of the sensor;

(6) by determining the presence of the gap Ga of the assist stator 341(441) and adjusting a clearance of the gap Ga, it is possible to correctand alter output characteristics of the sensor; and

(7) since both of the main stator 321 (421) and the assist stator 341(441) are manufactured by press operations, it is possible to producethe sensor in a low price.

FIG. 13 is a perspective view typically showing the non-contact positionsensor having its part developed, in accordance with a fifth embodimentof the present invention. FIG. 14 shows a top view (FIG. 14( a)), alongitudinal sectional/front view (FIG. 14( b)) and a bottom view (FIG.14)) of the sensor. In these figures, elements similar to those of FIG.1 are indicated with the same reference numerals plus four hundredsrespectively, and their overlapped descriptions are eliminated.

In a main stator 521 of this non-contact position sensor 500, atransverse wall (main arm) 523 continuing to a substantial upper halfpart of one opposed wall 522 is formed to extend over the other opposedwall 524 and further, the transverse wall 523 and one edge of theopposed wall 524 are adjacent to each other through a gap Gm.

This gap Gm is formed uniformly throughout upper and lower ends of thetransverse wall (main arm) 523. In the main stator 521, a transversewall (auxiliary arm) 525 continuing to a middle but slightly lower partof the other opposed wall 524 is formed to extend up to the opposed wall522 and further, the transverse wall (auxiliary arm) 525 and one edge ofthe opposed wall 522 are adjacent to each other through a not-shown gap.This gap is also formed uniformly throughout upper and lower ends of thetransverse wall (auxiliary arm) 525.

A hall sensor 531 is arranged in an appropriate position in a gap of themain stator 521, namely, the gap Gm of the main arm 523. For example, inview of arranging the sensor in a position close to a midpoint betweenboth ends of the main stator 521, it is desirable to arrange the sensor531 in the vicinity of the lower end of the main arm 523 in FIGS. 13 and14. In this way, on the ground that the gap of the main stator 521, thatis, the gap Gm of the main arm 523 is provided to accommodate the hallsensor 531, it is preferable that the gap Gm is formed to have aclearance as small as it can accommodate the sensor 531 although the gapGm appears to be remarkably broad in the figure.

An assist stator 541 as a magnetic flux leakproof member 540 is formedby opposed walls 542, 544 whose side edges are connected with each otherthrough a transverse wall 543 integrally and therefore, the assiststator 541 is constructed as an integral part having no gap Ga.Additionally, the assist stator 541 is formed so that a lower part ofthe transverse wall 543 is level with those of the opposed walls 542,544 without removing the lower part of the transverse wall 543.

The non-contact position sensor 500 like this can detect a position of amagnet 511 in a non-contact manner since the hall sensor 531 detectsmagnetic flux corresponding to an entrance percentage of the magnet 511in entering an area between the opposed walls 522, 524 of the mainstator 521, the magnet 511 being movable throughout the area between theopposed walls 522, 524 of the main stator 521 and a sequent area betweenthe opposed walls 542, 544 of the assist stator 541.

Again, this non-contact position sensor 500 is preventive of fluxleakage since all flux generated from a part of the magnet 511 enteringthe area between the opposed walls 522, 524 of the main stator 521passes through a magnetic path formed by the main stator 521.

While, since all flux generated from a part of the magnet 511 enteringthe area between the opposed walls 542, 544 of the assist stator 541passes through a magnetic path formed by the assist stator 541, fluxleakage is prevented as well.

Thus, assuming that the moving direction of the magnet 511 isrepresented by Z-direction, any offset of the magnet 511 in X-directionor Y-direction perpendicular to the Z-direction would not influence onthe magnetic paths, thereby causing no change in detection outputs ofthe hall sensor 531.

FIG. 15 is a perspective view typically showing the non-contact positionsensor having its part developed, in accordance with a sixth embodimentof the present invention. In the figure, elements similar to those ofFIG. 13 are indicated with the same reference numerals plus one hundredrespectively, and their overlapped descriptions are eliminated.

In this non-contact position sensor 600, a slider 610 comprises a sliderbody 612 accommodating a magnet 611 and a shaft 613 extending from theslider body 612 downwardly. Further, in an assist stator 641 as amagnetic flux leakproof member 640, a transverse wall 643 extending fromone edge of one opposed wall 642 toward the other opposed wall 644 andanother transverse wall 645 extending from one edge of the other opposedwall 644 toward the opposed wall 642 are arranged close to each otherthrough a gap Ga at a midpoint between the opposed walls 642, 644.Additionally, in the assist stator 641, its lower parts extending fromthe transverse walls 643, 645 to the opposed walls 642, 644 areeliminated.

A hall sensor 631 is arranged in an appropriate position in a gap of amain stator 621, namely, a gap Gm of a main arm 623. For example, inview of arranging the sensor in a position close to a midpoint betweenboth ends of the main stator 621, it is desirable to arrange the sensor631 in the vicinity of the lower end of the main arm 623 in FIG. 15. Inthis way, on the ground that the gap of the main stator 621, that is,the gap Gm of the main arm 623 is provided to accommodate the hallsensor 631, it is preferable that the gap Gm is formed to have aclearance as small as it can accommodate the sensor 631 although the gapGm appears to be remarkably broad in the figure.

The non-contact position sensor 600 like this can detect a position ofthe magnet 611, namely, both positions of the slider body 612 and theshaft 613 in a non-contact manner since the hall sensor 631 detectsmagnetic flux corresponding to an entrance percentage of the magnet 611in entering an area between the opposed walls 622, 624 of the mainstator 621, the magnet 611 being movable throughout the area between theopposed walls 622, 624 of the main stator 621 and a sequent area betweenthe opposed walls 642, 644 of the assist stator 641.

Again, this non-contact position sensor 600 is preventive of fluxleakage since all flux generated from a part of the magnet 611 enteringthe area between the opposed walls 622, 624 of the main stator 621passes trough a magnetic path formed by the main stator 621.

While, since all flux generated from a part of the magnet 611 enteringthe area between the opposed walls 642, 644 of the assist stator 641passes through a magnetic path formed by the assist stator 641, fluxleakage is prevented as well.

Thus, assuming that the moving direction of the magnet 611 isrepresented by Z-direction, any offset of the magnet 611 in X-directionor Y-direction perpendicular to the Z-direction would not influence onthe magnetic paths, thereby causing no change in detection outputs ofthe hall sensor 631.

FIG. 16 is a sectional view showing one example where the non-contactposition sensor 600 of FIG. 15 is applied to a position sensor for EGRvalve. This position sensor 650 for EGR valve includes the main stator621 and the assist stator 641 held by a stator holder 651 provided in asensor body. In the sensor 650, since the slider 610 accommodating themagnet 611 moves up and down in the figure, the hall sensor 631 detects,at its detecting position 632, a position of the magnet 611, that is,both positions of the slider body 612 and the shaft 613. In the figure,reference numeral 652 designates a connector terminal for connecting aterminal of the hall sensor 631.

Provided that vertical widths of the main arms 523, 623 are respectivelyequal to vertical width of the auxiliary arms 525, 625 and arerelatively wide (e.g. 4.5 mm) and that intervals between both arms (e.g.3 mm), FIG. 17 includes graphs showing a comparison of hysteresischaracteristics (FIG. 17( a)) of the non-contact position sensor 500using the integral-type assist stator 541 having no gap Ga withhysteresis characteristics (FIG. 17( b)) of the non-contact positionsensor 600 using the separation-type assist stator 641 having the gap Ga(e.g. gap Ga=1.5 mm).

In the sensor using the integral-type assist stator 541 shown in FIG.17( a), the hysteresis is large within a range of high stroke and thelinearity of output is curved in chevron. While, in the sensor using theseparation-type assist stator 641 shown in FIG. 17( b), it is found thatthe hysteresis in a range of high stroke is reduced remarkably andfurthermore, the linearity of output is corrected especially in anbackward stroke of the slider, while the chevron-shaped characteristicsin an outward stroke of the slider still remains.

On condition of employing the separation-type assist stator 641 of FIG.17( b), FIG. 18 is a graph showing the hysteresis characteristics of thenon-contact position sensor 600 where the vertical width of theauxiliary arm 625 is narrowed (e.g. from 4.5 mm to 2 mm). In case ofthis non-contact position sensor, since the hysteresis drops to gonegative in the whole operating range, it is found that an excessivedescent in hysteresis occurs. Further, it is also found that there islittle or no change in the chevron-shaped characteristics during theoutward stroke of the slider.

On condition of employing the separation-type assist stator 641 of FIG.17( b), FIG. 19 is a graph showing the hysteresis characteristics of thenon-contact position sensor 600 where an interval between the main arm623 and the auxiliary arm 625 is narrowed (e.g. from 3 mm to 2 mm). Thisnon-contact position sensor exhibits a positive hysteresis in the wholeoperating range and furthermore, a value of hysteresis gets smallerremarkably. Additionally, it is found that the linearity is corrected tochange its chevron-shaped characteristics to flat one.

According to the above-mentioned non-contact position sensors 500, 600;

(1) with the use of the assist stators 541, 641, it is possible toprevent flux from leaking out to the outside;

(2) with the use of the assist stators 541, 641, it is possible todetect the positions of the magnets 511, 611 within their entireoperation ranges appropriately;

(3) it is possible to provide sensors that are compact in respectivemoving directions of the magnets 511, 611 in relation to their movingspans;

(4) with the use of the main arms 523, 623 and the auxiliary arms 525,625, it becomes possible to displace respective detection positions fromcenters between both ends of the main stators 541, 641, allowing thehall sensors 531, 631 to be arranged in appropriate positions onconsideration of convenience of production.

(5) by altering the vertical widths of the auxiliary arms 525, 625 whilemaintaining constant vertical widths of the main arms 523, 623, it ispossible to change a magnitude of hysteresis.

(6) by adjusting an interval between the main arm 523 (623) and theauxiliary arm 525 (625), it is possible to correct and alter outputcharacteristics of the sensor;

(7) by adjusting a balance between the gap Gm of the main stator 521(621) and the gap Gma formed between the main stator 521 (621) and theassist stator 541 (641), it is possible to correct and alter outputcharacteristics of the sensor;

(8) by determining the presence of the gap Ga of the assist stator 541(641) and adjusting a clearance of the gap Ga, it is possible to correctand alter output characteristics of the sensor; and

(9) since both of the main stator 521 (621) and the assist stator 541(641) are manufactured by press operations, it is possible to producethe sensor in a low price.

Tendencies of various characteristics mentioned above are shown in FIGS.20 to 24, in abstraction and summary. FIG. 20 illustrates an influenceof the position of each detecting part on linearity, representing thatthere exists a detecting position exhibiting the best characteristics atthe center of the main stator. Additionally, it is found that detectingpositions deviated from the center of the main stator representchevron-shaped characteristics.

FIG. 21 shows a relationship between the position of the detecting partand the hysteresis. From the figure, it is found that if the detectingposition is deviated from the center of the main stator, then a gradientof hysteresis changes centering on a center of characteristic range.

FIG. 22 illustrates an influence of the gap Gma between the main statorand the assist stator on linearity. From the figure, it is found that tonarrow the gap between the main stator and the assist stator causes bothends of a chevron-shaped linearity to get close to a straight line.

FIG. 23 shows a relationship between the gap between the main stator andthe assist stator and the hysteresis, representing that to narrow thegap between the main stator and the assist stator causes the hysteresisto be decreased. From the figure, it is also found that an influence ofnarrowing gets larger especially in a lower-operating range and in anextreme case, the hysteresis becomes negative.

FIG. 24 shows a relationship between the gap of the assist stator andthe hysteresis. From the figure, it is found that the broader the gap ofthe assist stator gets, the smaller the hysteresis in the entire rangegets in parallel translation. If the gap is broadened excessively, thehysteresis becomes negative in the entire range. Additionally, althoughit is not shown, there is no likelihood of an influence of the gap ofthe assist stator on the linearity.

FIG. 25 includes an entire perspective view (FIG. 25( a)) typicallyshowing the non-contact position sensor in accordance with a seventhembodiment of the present invention and a perspective view (FIG. 25( b))of a substantial part of the sensor. FIG. 26 shows a top view (FIG. 26(a)), a side view (FIG. 26( b)) and a bottom view (FIG. 26( c)) of thesensor.

This non-contact position sensor 700 comprises a substantially-flatslider 710, a substantially-flat main stator 721 as a stator 720, a hallsensor 731 as a magnetically-sensitive sensor 730 and asubstantially-flat assist stator 741 as a magnetic flux leakproof member740.

The slider 710 comprises a magnet 711 and an armature 712 and isconstructed so as to move along its longitudinal direction (a verticaldirection shown with an arrow of FIG. 25( a)) linearly.

The magnet 711 is composed of a pair of substantially-flat plates whichhave respective front and back faces of N-pole and S-pole and extend amoving direction of the slider 710 and of whose respective one sideshaving different polarities are joined to each other side by side.

The magnet 711 like this is arranged on the front side of the slider710, that is, on a side opposing the main stator 721 and the assiststator 741 through a required clearance. While, on the backside of theslider 710, the armature 712 is arranged in contact with the magnet 711.Therefore, a front face of the magnet 711 opposes the main stator 721and the assist stator 741, while a back face of the magnet 711 comes incontact with the armature 712.

The main stator 721 consists of magnetic bodies and includes separationwalls 726, 727 opposing the magnet 711, which are arranged close to eachother through a gap Gm at the center of the stator 721. This gap Gm isformed uniformly between both ends of the main stator 721 (upper andlower ends in FIGS. 25 and 26) along a moving direction of the magnet711. The main stator 721 like this can be manufactured by pressing e.g.a plate material of magnetic material whose magnetic resistance is assmall as possible.

The hall sensor 731 is arranged in an appropriate position in the gap Gmof the main stator 721. For example, it is desirable to arrange thesensor 731 at a midpoint between both ends of the main stator 721 (inFIGS. 25 and 26, at a center level between the upper end and the lowerend of the main stator 721). In this way, on the ground that the gap Gmof the main stator 721 is provided to accommodate the hall sensor 731,it is preferable that the gap Gm is formed to have a clearance as smallas it can accommodate the sensor 731.

The assist stator 741 consists of a magnetic body and opposes the magnet711. The assist stator 741 like this can be manufactured by pressinge.g. a plate material of magnetic material whose magnetic resistance isas small as possible.

The main stator 721 and the assist stator 741 are arranged close to eachother through a gap Gma along the moving direction of the magnet 711. InFIGS. 25 and 26, since the assist stator 741 is positioned above themain stator 721, a spatial area where the assist stator 741 opposes themagnet 711 is formed above a spatial area where the main stator 721opposes the magnet 711 continuously.

The non-contact position sensor 700 constructed above can detect aposition of the magnet 711 in a non-contact manner since the hall sensor731 detects magnetic flux corresponding to an entrance percentage of themagnet 711 in entering the area opposed by the main stator 721, themagnet 711 being movable throughout the area opposed by the main stator721 and the sequent area opposed by the assist stator 741.

Again, this non-contact position sensor 700 is preventive of fluxleakage since all flux generated from the front face of a part of themagnet 711 entering the area opposed by the main stator 721 passestrough a magnetic path formed by the main stator 721. At this time,since flux generated from the back face of the same part of the magnet711 passes through a magnetic path formed by the armature 712, fluxleakage is prevented.

While, since all flux generated from the front face of a part of themagnet 711 entering the area opposed by the assist stator 741 passesthrough a magnetic path formed by the assist stator 741, flux leakage isprevented as well. At this time, since flux generated from the back faceof the same part of the magnet 711 passes through a magnetic path formedby the armature 712, flux leakage is prevented.

Thus, assuming that the moving direction of the magnet 711 isrepresented by Z-direction, any offset of the magnet 711 in X-directionor Y-direction perpendicular to the Z-direction would not influence onthe magnetic paths, thereby causing no change in detection outputs ofthe hall sensor 731.

FIG. 27 includes an entire perspective view (FIG. 27( a)) typicallyshowing the non-contact position sensor in accordance with an eighthembodiment of the present invention and a perspective view (FIG. 27( b))of a substantial part of the sensor. In this figure, elements similar tothose of FIG. 25 are indicated with the same reference numerals plus onehundred respectively, and their overlapped descriptions are eliminated.

This non-contact position sensor 800 includes a stator 820, amagnetically-sensitive sensor 830 and a magnetic flux leakproof member840 all arranged inside a slider 810 curved substantially in an arc.

That is, the non-contact position sensor 800 comprises the slider 810, amain stator 821 having a substantially arc-shaped curved facecorresponding to an arc shape of the slider 810, a hall sensor 831 andan assist stator 841 having a substantially arc-shaped curved facecorresponding to the arc shape of the slider 810.

The non-contact position sensor 800 constructed above can detect aposition of the magnet 811 in a non-contact manner since the hall sensor831 detects magnetic flux corresponding to an entrance percentage of themagnet 811 in entering an area opposed by the main stator 821, themagnet 811 being movable throughout the area opposed by the main stator821 and a sequent area opposed by the assist stator 841.

Again, this non-contact position sensor 800 is preventive of fluxleakage since all flux generated from the front face of a part of themagnet 811 entering the area opposed by the main stator 821 passesthrough a magnetic path formed by the main stator 821. At this time,since flux generated from the back face of the same part of the magnet811 passes through a magnetic path formed by an armature 812, fluxleakage is prevented.

While, since all flux generated from the front face of a part of themagnet 811 entering the area opposed by the assist stator 841 passesthrough a magnetic path formed by the assist stator 841, flux leakage isprevented as well. At this time, since flux generated from the back faceof the same part of the magnet 811 passes through a magnetic path formedby the armature 812, flux leakage is prevented.

Thus, assuming that the moving direction of the magnet 811 along its arcis represented by Z-direction, any offset of the magnet 811 inX-direction or Y-direction perpendicular to the Z-direction would notinfluence on the magnetic paths, thereby causing no change in outputs ofthe hall sensor 831.

FIG. 28 includes an entire perspective view (FIG. 28( a)) typicallyshowing the non-contact position sensor in accordance with a ninthembodiment of the present invention, a perspective view (FIG. 28( b)) ofa substantial part of the sensor and a perspective view (FIG. 28( c)) ofthe substantial part at a different angle. In this figure, elementssimilar to those of FIG. 27 are indicated with the same referencenumerals plus one hundred respectively, and their overlappeddescriptions are eliminated.

This non-contact position sensor 900 includes a stator 920, amagnetically-sensitive sensor 930 and a magnetic flux leakproof member940 all arranged outside a slider 910 curved substantially in an arc.

That is, the non-contact position sensor 900 comprises the slider 910, amain stator 921 which is substantially arc-shaped and curvedcorresponding to an arc shape of the slider 910, a hall sensor 931 andan assist stator 941 which is substantially arc-shaped and curvedcorresponding to the arc shape of the slider 910.

The non-contact position sensor 900 constructed above can detect aposition of the magnet 911 in a non-contact manner since the hall sensor931 detects magnetic flux corresponding to an entrance percentage of themagnet 911 in entering an area opposed by the main stator 921, themagnet 911 being movable throughout the area opposed by the main stator921 and a sequent area opposed by the assist stator 941.

Again, this non-contact position sensor 900 is preventive of fluxleakage since all flux generated from the front face of a part of themagnet 911 entering the area opposed by the main stator 921 passestrough a magnetic path formed by the main stator 921. At this time,since flux generated from the back face of the same part of the magnet911 passes through a magnetic path formed by an armature 912, fluxleakage is prevented.

While, since all flux generated from the front face of a part of themagnet 911 entering the area opposed by the assist stator 941 passesthrough a magnetic path formed by the assist stator 941, flux leakage isprevented as well. At this time, since flux generated from the back faceof the same part of the magnet 911 passes through a magnetic path formedby the armature 912, flux leakage is prevented.

Thus, assuming that the moving direction of the magnet 911 along its arcis represented by Z-direction, any offset of the magnet 911 inX-direction or Y-direction perpendicular to the Z-direction would notinfluence on the magnetic paths, thereby causing no change in outputs ofthe hall sensor 931.

INDUSTRIAL APPLICABILITY

As mentioned above, the present invention provides a non-contactposition sensor where a magnetically-sensitive sensor in the statordetects a position of a slider by an entrance percentage of the sliderin entering an area where the slider with a magnet can move whilekeeping a required clearance against a stator formed by a magnetic bodyand further, the non-contact position sensor includes a magnetic fluxleakproof member for preventing flux, which is generated from a part ofthe magnet that does not enter the area, from leaking out to the stator.Therefore, according to the present invention, without adopting aclearance between the moving magnet and the stator as a magnetic path,it is possible to effectively utilize a length of the magnet in themoving direction in order to detect a position of the magnet.

1. A non-contact position sensor comprising: a slider having a magnethaving a front face along a longitudinal direction of the magnet thathas one polarity and a back face along the longitudinal direction of themagnet that has an opposite polarity; a main stator consisting of amagnetic body having a first pair of opposed walls forming an area inwhich the slider enters while keeping a predetermined clearance, thefirst pair of opposed walls corresponding to the front and back faces ofthe magnet, and a first gap continuing into the opposed walls; amagnetically-sensitive sensor arranged in the first gap to detect aposition of the slider corresponding to a percentage of the magnetentering the area; and an assist stator for preventing magnetic flux,which is generated in a part of the magnet that does not enter the area,from leaking out to the main stator, wherein the assist stator has asecond pair of opposed walls corresponding to front and back faces ofthe part of the magnet that does not enter the area and transverse wallsextending from the second pair of opposed walls which are separated fromeach other through a second gap formed between the transverse walls,wherein the first and second gaps are formed uniformly along a movingdirection of the slider, respectively.
 2. The non-contact positionsensor of claim 1, wherein the magnetically-sensitive sensor is providedin a direction perpendicular to a moving direction of the slider.
 3. Anon-contact position sensor comprising: a slider having a magnet havinga front face along a longitudinal direction of the magnet that has onepolarity and a back face along the longitudinal direction of the magnetthat has an opposite polarity; a main stator consisting of a magneticbody having a first pair of opposed walls forming a first area in whichthe slider enters while keeping a predetermined clearance, the firstpair of opposed walls corresponding to the front and back faces of themagnet, and a first gap continuing into the opposed walls; an assiststator consisting of a magnetic body having a second pair of opposedwalls forming a second area which allows the slider to move whilekeeping a predetermined clearance and transverse walls extending fromthe second pair of opposed walls which are separated from each otherthrough a second gap formed between the transverse walls, wherein thereis a third gap between the assist stator and the main stator; and amagnetically-sensitive sensor arranged in the first gap to detect aposition of the slider corresponding to a percentage of the magnetentering the first area, wherein the first and third gaps are formeduniformly along a moving direction of the slider, respectively.
 4. Thenon-contact position sensor of claim 3, wherein themagnetically-sensitive sensor is provided in a direction perpendicularto a moving direction of the slider.